Synthetic gene regulation in cyanobacteria

Cyanobacteria are appealing hosts for green chemical synthesis due to their use of light and carbon dioxide. To optimize product yields and titers, specific and tunable regulation of the metabolic pathways is needed. Synthetic biology has increased and diversified the genetic tools available for biological process control. While early tool development focused on commonly used heterotrophs, there has been a recent expansion of tools for cyanobacteria. CRISPR-Cas9 has been used to edit the genome of cyanobacterial strains, while transcriptional regulation has been accomplished with CRISPR interference and RNA riboswitches. Promoter development has produced a significant number of transcriptional regulators, including those that respond to chemicals, environmental signals, and metabolic states. Trans-acting RNAs have been utilized for posttranscriptional and translational control. The regulation of translation initiation is beginning to be explored with ribosome binding sites and riboswitches, while protein degradation tags have been used to control expression levels. Devices built from multiple parts have also been developed to create more complex behaviors. These advances in development of synthetic cyanobacterial regulatory parts provide the groundwork for creation of new, even more sophisticated bioprocess control devices, bolstering the viability of cyanobacteria as sustainable biotechnology platforms.